1. Field of the Invention
The present invention relates to an image processing method for determining the quality of dispersion of glass fibers in a thermoplastic resin preform layer where the glass fibers have been introduced as glass fiber bundles. The present invention also relates to a thermoplastic resin preform layer comprising a plurality of individual glass fibers and some degree of undispersed glass fiber bundles intimately mixed with a plurality of discrete thermoplastic fibers characterized by this method.
2. Description of the Related Art
Glass fiber-reinforced preform sheets, or layers, are commercially valuable materials used in the compression molding industry for fabrication of automotive components, such as bumper beams and structural panels. Such preform sheets generally comprise a blend of thermoplastic resin with glass-reinforcing fiber bundles, or tows. Typically, the preform sheets are trimmed to appropriate dimensions, are preheated to melt the thermoplastic component, and are then placed in a matched metal die for forming under heat and pressure. A desirable goal is the ability to compression mold panels from wet-formed glass reinforced thermoplastic preform sheets, such that the resulting molded plaques have sufficient surface smoothness for applications such as exterior automotive panels.
Glass fiber-reinforced resin laminates are known in the art, as exemplified by U.S. Pat. No. 3,063,883 to Brissette. This patent discloses a glass fiber preform mat for use in the production of reinforced resin laminates, which will completely wet-out with an impregnating resin. Brissette is not concerned with compression molding the laminate into a composite plaque and accordingly, is not concerned with the surface uniformity of the molded plaque.
Although Brissette does disclose an even dispersion of co-polymeric fibers with glass fibers, it contains no discussion of the degree of dispersion of the glass fibers. Instead, Brissette makes a visual determination that an intimate fiber blend is achieved, which is unreliable, since it is subjective. In Brissette, there is no quantification of the degree of dispersion of glass fibers. Indeed, most any dispersion technique will leave some small fraction of the glass fiber as partially undispersed bundles. Since even a small percentage of glass fiber bundles can render a preform sheet unusable for applications requiring a very smooth surface in a molded plaque, it is highly desirable to define a technique which provides a reliable, quantitative measurement of dispersion.